Uranium processing



2,953,432 Patented Sept. 20, 1960 URANIUM PROCESSING James L. Hart andRobert E. Reusser, Bartlesville, kla.,

assignors to Phillips Petroleum Company, a corporation of Delaware NoDrawing. Filed Nov. 13, 1958, Ser. No. 773,553

10 Claims. (Cl. 23-145) This invention relates to the processing ofuranium. More particularly, the invention relates to a method forrecovering uranium in a more concentrated form from an aqueousuranium-bearing solution.

In the processing of uranium ores, various methods are employed forextracting the uranium values into aqueous solutions by employing eitheran acidic or a basic leaching solution to dissolve the uranium valuesfrom the ore. There is often required a simultaneous oxidation of theore in order to convert the uranium values to a soluble form. In anycase, the resulting uranium solutions are usually quite diluted so thatlarge volumes of materials must be handled in order to concentrate theuranium values for further recovery.

It is an object of the invention to recover uranium in a moreconcentrated form from acidic or basic aqueous uranium solutions. Otherobjects, as well as advantages and aspects, of the invention will becomeapparent from a consideration of the accompanying disclosure.

In accordance with the process of the invention an acidic or basicsolution containing dissolved uranium values is treated with a selectedorganic liquid, and the resulting mixture separated into two liquidlayers, the water rich liquid layer containing dissolved uranium in ahigher concentration than the original solution. The liquid phasecontaining the dissolved uranium usually amounts to 0.5 to about 30percent of the total volume.

Prior art processes which have utilized certain organic liquids for theconcentration of uranium solutions have employed these liquids asextractants into which uranium is dissolved. In the present process theuranium is rejected from the organic liquid rich layer and isconcentrated in the water rich layer in a substantially smaller volumeof water than originally. Thus, the organic liquid employed is a liquidwhich is quite water soluble. The uraniumrich phase can be recoveredfrom the concentrated solution by various procedures, which will bediscussed hereafter.

The aqueous uranium-bearing liquors which are beneficiated according tothe process of the invention are acidic or basic systems. The acidicsolutions must have a pH in the range from about 0.5 to 5, and the basicsolutions must have a pH of about 8 or higher. If the pH is in the rangeof above about and below about 8, at least a portion of the uranium isgenerally precipitated. In the case of the basic solutions the upperlimit of pH of the solution to be treated is, as stated, 8 or above, butit is also preferably below some higher pH at which uranium precipitatesfrom the solution; this upper pH is a variable and depends to a largeextent upon the uranium concentration. Generally the upper limit of pHof 11 is applicable in all cases, but in the case of uraniumconcentrations of 300 mg/liter (expressed as U 0 this upper limit can beas high as pH 13.

The amount of the selected organic liquid employed is from 0.5 to 3volumes for each volume of water in the aqueous uranium-bearing liquid,more usually from 0.75 to 2 volumes of organic liquid for each volume ofwater.

The preferred organic liquid is acetone, but ethyl alcohol, n-propylalcohol, and isopropyl alcohol are also applicable. Surprisingly, anumber of other organic liquids have not been found to be eifective,such as methyl ethyl ketone, ethyl acetate, cyclohexanone, diethylCellosolve, dimethyl sulfoxide, glycerol, methyl alcohol, and amylalcohol. In the acid system there is also employed in the aqueousuranium solution from about 20 to grams of a soluble inorganic salt perliter of water in the solution in an amount in this range effective topromote the rejection of the uranium values from the organic liquidrichphase by a salting out effect. 7

Any suitable inorganic salt can be employed in the acid system to effectthe salting out. A particularly useful group of salts has been found tobe sodium sulphate, magnesium sulphate, zinc sulphate and aluminumsulphate. Some other salts which can be mentioned are sodium chloride,ammonium sulphate, Na PO K PO and Na H PO The uranium values can berecovered from the uranium-rich liquid phase by various procedures. Inone method, addition of an alkali metal hydroxide, such as sodiumhydroxide is used to precipitate uranium. The precipitated uranium canbe removed by filtration. This is a conventional and Well knownprocedure. In other well known methods the uranium can be extracted fromthe concentrated aqueous solution by an organic solvent such as kerosenecontaining an alkyl phosphate or an amlne.

The following examples are illustrative of the invention, but are not tobe taken as limiting thereof.

Example I Uranyl nitrate, UO (NO -6H O, in amount of 3.623 parts byweight was dissolved in about 950 parts by weight of water and broughtto a pH of 1.5 by addition of 4 parts by weight of a 50 percent byweight sulfuric acid solution. The solution was diluted with water.Analysis of the solution gave: dissolved uranium, expressed as U O =2.02g./liter; and sulfate ion, expressed as sodium sulfate: 2.65 g./liter.

Aliquots of this acidic uranium solution were mixed with various amountsof anhydrous sodium sulfate and then with acetone in a volume ratio ofacetone to water of about 1.3. Observations were made of the volumepercent of the acetone rich upper layer and the greenishcolored, waterrich, heavy layer which separated. From analysis of the upperacetone-water layer the percentage uranium which was separated in thelower liquid phase was obtained. These results were as follows:

Heavy Liquid Layer, Vol. Percent Sodium Sulfate Added, g./l.

1 Grams per liter of aqueous uranium solution on an acetone-free basis.2 N 0 phase separation.

When only 10 gram sodium sulfate per liter was added no phase separationoccurred. Increase in the sodium sulfate to 25 g./litcr of the initialuranium solution resulted in the separation of a uranium-rich phasecontaining 61.63 percent of the uranium. The percentage uraniumrecovered in this manner was increased to 82.8 and 89.4 percent byincrease in the amount of sulfate added to 40 and 55 grams per liter ofthe acid uranium solution which was used.

3 Example 11 Uranium-rich Acetone to Water Volume Ratio Phase Sepa-Uranium Separated, Vol. rated, Percent Percent None 6 5 50.0 140 51.5 1497. 8

These data show that when the acetone to water ratio is only 0.26 therewas no separation of a uranium-rich phase. For acetone to water ratiosof 0.5 and higher, phase separation did occur with a concentration ofthe uranium in the liquid phase which separated. The uranium recoveryincreased from 50 to 97.8 percent by increase in the volume ratio ofacetone to water from 0.5 to 1.03.

Example III A uranium-containing liquor was prepared by extraction of anore which had been ground to minus 20 mesh; this ore contained 0.56weight percent uranium, expressed as U Several batches were extractedand the clarified, liquors from the several runs were combined. For eachextraction the slurry contained about 50 percent by weight of ore. Theextraction was efiected by the use of 110 to 175 pounds of sulfuric acidper ton of ore. Manganese dioxide (10 lb./ton) and air (470 cu. ft. perton) were used as oxidants.

A 40 volume portion of the acidic uranium solution (pH about 1) wasmixed with a 50 volume portion of acetone. The solution, which wascloudy with a small amount of solid matter, was clarified by filtration.To the clarified liquor there was added volumes of an aqueous Na SOsolution containing 440 grams of Na SO per liter of water, whereuponthere separated about 5 volumes of a heavy, greenish-colored lowerliquid phase. Theuranium in this colored liquid phase Was extracted intokerosene containing a dissolved amine. From two extractions, there wasrecovered 85.3 percent of the total uranium initially present in theliquor. Thus, the uranium was largely concentrated in thegreenish-colored liquid phase which was 12.5 percent of the volume ofthe initial aqueous system.

The kerosene-amine solution employed in this example contained aboutvolume percent of a mixture of amines having the following structuralformula:

where the total carbon atoms in R+R+R"=11-14 and R, R and R" are eachalkyl groups.

Example IV A uranium-bearing ore (0.18% U 0 was extracted with anaqueous carbonate leach solution consisting of 50 g./liter of sodiumcarbonate and 15 g./liter of sodium bicarbonate, employing the leachsolution in the ratio of 2444 lbs./ton of ore. The extraction waseflected at C. for 18 hours using as oxidants air and a solid oxidant(potassium permanganate). The uranium values were dissolved by thisprocess in the form of the sodium uranyl tricarbonate complex. Theresulting liquor from the oxidative extraction was found to contain thefollowing: Uranium, expressed as U 0 1.4 g./liter; sodium carbonate,44.6 g./ liter; sodium bicarbonate, 15.8 g./liter; and sulfate,expressed as sodium sulfate, 7.95 g./liter. The pH of the solution wasabout 9.8.

One volume of the alkaline uranium bearing solution was mixed with anequal volume of acetone whereupon there separated 0.151 volume of aheavy uranium-rich liquid phase having a green coloration. This phasewas separated from the acetone-rich upper layer by decantation, and wastreated with 10. 8 volumes of a sodium hydroxide solution (50 wgt.percent NaOH). The mixture was digested 7 hours at 60 C. to eifectprecipitation of the uranium as sodium diuranate. The yellow cake whichformed was removed by filtration and washed with water. The purity ofthe yellow cake, expressed as percentage sodium diuranate was 88percent. The uranium which was recovered as a yellow cake was about 96percent of the total amount present in the original alkaline solution.Thus, the liquid phase which separated effected not only a concentrationof the uranium in the heavy, water-rich liquid phase but also efiected avery high recovery of the uranium. The alkaline liquor which wasobtained from filtration of the yellow cake was found to contain about1.1 percent of the uranium.

The acetone rich layer which was recovered after separation of theuranium-rich phase amounted to 1.77 volumes per volume of originalalkaline uranium bearing solution. By distillation, there was recovered1.005 volumes of an acetone solution containing 0.992 volume acetone and0.013 volume of Water. Thus, the acetone recovery was at least 99percent. The aqueous residue left from distillation of the acetonecontained 3.0 percent of the uranium.

Example V A solution was prepared by dissolving 4.96 parts by weight ofsodium uranate, Na UO in about 1500 parts by weight of water and adding7.9 parts by weight of 98 percent sulfuric acid. The solution was thendiluted with water. The pH was found to be 1.5. By analysis the solutionwas found to contain uranium, expressed as U 0 in the amount of 1.94grams per liter.

Portions of the acidic solution were taken and sodium sulfate in amountof 50 grams per liter were dissolved in each, except run 4. Eachsolution was mixed with acetone in amounts from 1 to 3 volumes ofacetone per volume of the aqueous solution. Observations were then madeof the amount of the uranium rich, aqueous liquid phase which separated.The results are summarized in the tabulation below:

Acetone/Solution Ratio Liquid Phase Separated, Vol. Percent of TotalPWN!" ocoo 1 Sodium sulfate omitted.

Example VI For these runsweighed amounts of sodium uranate weredissolved by mixing with water and sufficient 98 percent sulfuric acidto achieve solubilization of the salt. Each solution was mixed withsodium sulfate and diluted to a volume of 20 volumes so that the sodiumsulfate added was suificient to give a concentration of 50 grams perliter. The pH of these solutions was between 1.9 and 2.1. Finally, 25volumes of acetone was mixed with each solution so that the acetone towater volume ratio was about 1.3. Observations were then made of theamount of the heavy, uranium containing, green colored liquid phasewhich separated from each system. The results were as follows:

The foregoing example illustrates the concentration of uranium valuesaccording to the present process, from an aqueous solution containingvarying amounts of uranium. In the process of the invention uraniumsolutions containing much less than 2 grams U can be treated. Also,uranium solutions containing more than 100 grams per liter can betreated. The process is most often applied, however, to solutionscontaining uranium, expressed as U O of 100 grams per liter or less,most often grams per liter or less.

Example VII The following runs were made with an acidicuraniumcontaining solution prepared by dissolving sodium uranate inwater so as to give a uranitun concentration, expressed as U O of about2.0 grams per liter together with sufiicient sulfuric acid to give a pHof 1.5. To ml. portions of this acidic solution various inorganic saltsand organic liquids were added in amounts as stated in this tabulation.Observations were then made as to the amounts of the heavy,greenish-colored liquid phase separated from each system. In thetabulation, the amount of salt added is expressed in terms of grams perliter of the acidic, aqueous uranium solution. The amount of organicliquid is expressed in terms of ratio of the volume of organic liquid tothe acidic uranium solution. The results are shown in the followingtable:

Example VIII For these runs a simulated carbonate leach liquor wasprepared by dissolving 9.9184 grams Na UO in 2 liters of distilled watercontaining 5.65 grams of concentrated (98 percent) sulfuric acid. Thissolution having a pH of 2.4 was treated with a water solution containing200 grams anhydrous sodium carbonate and 60 grams sodium bicarbonate toneutralize the acid and render the solution basic. The resulting uraniumsolution was diluted to 4 liters. Analysis of a portion of the solutionshowed the uranium content to be 1.93 grams (as U 0 per liter. The pH ofthe solution was about 9.8. For each run, the solution was diluted withan equal volume of the organic liquid and observations made of theheavy, greenish-colored liquid phase which separated.

Heavy Liquid Run No Organic Liquid Phase, Vol.

Percent Methyl ethyl ketone 50 Ethyl acetate 50 Oyelohexanone-.- 50Diethyl Oellosolve 65 Dimethyl SUlfOXlde 0 lyoerol 0 Ethyl alcohol. 4. 4Isopropyl alcohol 13 Propyl alcohol 30 10 Amy} alnnh nl 47 11 Methylalcohol 0 From the foregoing it will be seen that only ethyl, isopropyland propyl alcohols were eifective to concentrate the uranium in theheavy liquid phase. Thus, as to the other organic liquids employed therewas either no separate liquid phase formed or there was no concentrationin the heavy liquid phase. The slight concentration with amyl alcohol isinsignificant and of no value. It will be noted that, surprisingly,methyl alcohol is not effective.

Example IX The uranium solution used for these tests was prepared bymixing 9.9184 grams of Na UO in two liters of water and adding 7.5 gramsof concentrated sulphuric acid. The resulting uranium solution had a pHof 1.7. This solution was diluted with two liters of an aqueous solutioncontaining 200 grams of sodium carbonate and 60 grams of sodiumbicarbonate. The resulting solution was clarified by filtration and byanalysis was found to contain in grams per liter: 2.1U O 48.O9Na CO16.38NaHCO and 2.27Na SO Portions of this solution were admixed withacetone as shown in the tabulation below. Observations were made of thevolume percent of the heavy, uranium-rich phase which separated. Byanalysis of a portion of the supernatant liquid, the percentage of theuranium in the uranium-rich phase was determined. The results show thatthe uranium can be concentrated in the heavy phase which separates.

Heavy liquid Uranium in Acetone to solution ratio phase, volume heavyphase,

percent percent As will be evident to those skilled in the art, variousmodifications of this invention can be made or followed in the light ofthe foregoing disclosure and discussion without departing from thespirit and scope of the disclosure or from the scope of the claims.

We claim:

1. A process for recovering uranium in a more concentrated form fromaqueous uranium-healing solutions which comprises mixing said solutionwith a selected organic liquid and allowing the resulting mixture toseparate into two liquid phases, the heavier of which contains dissolveduranium values in a higher concentration than the original aqueoussolution, the original aqueous uranium-bearing solution being selectedfrom the group consisting of a basic solution having a pH in the rangefrom 8 to 11 and an acidic solution having a pH in the range from 0.5 to5, the volume ratio of said selected organic liquid to water in saidresulting mixture being in the range from 0.5 to 3, the organic liquidbeing selected from the group consisting of acetone, ethyl alcohol,npropyl alcohol and isopropyl alcohol; wherein said original acidicaqueous solution contains an amount of an inorganic salt in the rangefrom about 20 to grams per liter of water, said salt being selected fromthe group consisting of sodium sulfate, zinc sulfate, magnesium sulfateand aluminum sulfate.

2. A process of claim 11 wherein the volume ratio of uranium-bearingsolution, is an aqueous'solut-ion having a' pH in the range from 8 to11. 7 r

6. A process of claim 1 wherein said organic liquid is acetone. r

7. A process of claim 5 wherein said organicliquid is acetone.

9. A process of claim 5 wherein said organic liquid is ethyl alcohol.

10. A process of claim 5 wherein said organic liquid is n-propylalcohol.v

References Cited in the file of this patent UNITED STATES PATENTS Katzinet al.: AECD-2537, March 18, 1949, pages 1,

' 8. A process ofclaim 5 wherein said organic liquid 15 r isopropylalcohol. 7

Kimball et al. July 23, 1957 Clark et al. June 17, 1958 OTHER REFERENCES

1. A PROCESS FOR RECOVERING URANIUM IN A MORE CONCENTRATED FORM FROMAQUEOUS URANIUM-BEARING SOLUTIONS WHICH COMPRISES MIXING SAID SOLUTIONWITH A SELECTED ORGANIC LIQUID AND ALLOWING THE RESULTING MIXTURE TOSEPARATE INTO TWO LIQUID PHASES, THE HEAVIER OF WHICH CONTAINS DISSOLVEDURANIUM VALUES IN A HIGHER CONCENTRATION THAN THE ORIGINAL AQUEOUSSOLUTION, THE ORIGINAL AQUEOUS URANIUM-BEARING SOLUTION BEING SELECTEDFROM THE GROUP CONSISTING OF A BASIC SOLUTION HAVING A PH IN THE RANGEFROM 8 TO 11 AND AN ACIDIC SOLUTION HAVING A PH IN THE RANGE FROM 0.5 TO5, THE VOLUME RATIO OF SAID SELECTED ORGANIC LIQUID TO WATER IN SAIDRESULTING MIXTURE BEING IN THE RANGE FROM 0.5 TO 3, THE ORGANIC LIQUIDBEING SELECTED FROM THE GROUP CONSISTING OF ACETONE, ETHYL ALCOHOL,NPROPYL ALCOHOL AND ISOPROPYL ALCOHOL, WHEREIN SAID ORIGINAL ACIDICAQUEOUS SOLUTION CONTAINS AN AMOUNT OF AN INORGANIC SALT IN THE RANGEFROM ABOUT 20 TO 80 GRAMS PER LITER OF WATER, SAID SALT BEING SELECTEDFROM THE GROUP CONSISTING OF SODIUM SULFATE, ZINC SULFATE, MAGNESIUMSULFATE AND ALUMINUM SULFATE.